Internal and external separation of geomagnetic storms based on the ground observation network and its application to 3D-TDEM modeling of the conducting Earth
Spherical harmonics have been the useful tool not only for expanding the global distribution of the geomagnetic field but for separating the potential field into the internal and external origin. We extended the spherical harmonic analysis method to higher time resolution, say 1 hr 1 min, in order to describe the dynamic nature of the varying part of the magnetic field of our planet. A stochastic inversion scheme using singular-value decomposition was newly developed to yield hourly or one-minute values of the internal and external Gauss coefficients up to degree 6. The rapid spherical harmonic expansion was applied to the data from the global geomagnetic observatory network on land consisting of more than 100 stations, 62 of which were actually used in separating a series of geomagnetic storms occurred in November and December, 2001.It is also desirable to utilize the separated external geomagnetic field as three-dimensional sources. To achiev e this,we developed a three-dimensional global time domain geomagnetic field simulator that is capable of calculating theoretical internal geomagnetic fields in response to the given external field on heterogeneous spheres.Three-dimensional time domain electromagnetic inversion will be realized using the realistic three-dimensional source field, if we can recover a simulated internal field of a heterogeneous sphere that coincides well with the separated (i.e.,observed) internal field. Here we show results of the internal field simulation for three-dimensional spheres using the separated external field of an actual geomagnetic storm as source.
geomagnetic storms internal-external separation three-dimensional time domain EM spherical harmonics
TOH Hiroaki HAMANO Yozo
Graduate School of Science, Kyoto University, Kyoto, JAPAN IFREE, JAMSTEC, Yokosuka, JAPAN
国际会议
The 19th International Workshop on Electromagnetic Induction in the Earth(第十九届国际地球电磁感应学术研讨会)
北京
英文
889-894
2008-10-23（万方平台首次上网日期，不代表论文的发表时间）